Network Working Group S. Shimizu
Request for Comments: 3186 T. Kawano
Category: Informational K. Murakami
NTT Network Innovation Labs.
E. Beier
DeTeSystem
December 2001
Network Working Group S. Shimizu
Request for Comments: 3186 T. Kawano
Category: Informational K. Murakami
NTT Network Innovation Labs.
E. Beier
DeTeSystem
December 2001
MAPOS/PPP Tunneling mode
MAPOS/PPP隧道模式
Status of this Memo
本备忘录的状况
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
本备忘录为互联网社区提供信息。它没有规定任何类型的互联网标准。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (2001). All Rights Reserved.
版权所有（C）互联网协会（2001年）。版权所有。
IESG Note
IESG注释
This memo documents a way of tunneling PPP over Sonet over MAPOS networks. This document is NOT the product of an IETF working group nor is it a standards track document. It has not necessarily benefited from the widespread and in depth community review that standards track documents receive.
本备忘录记录了一种通过MAPOS网络通过Sonet传输PPP的方法。本文件不是IETF工作组的产品，也不是标准跟踪文件。它不一定从标准跟踪文件所接受的广泛深入的社区审查中获益。
Abstract
摘要
This document specifies tunneling configuration over MAPOS (Multiple Access Protocol over SONET/SDH) networks. Using this mode, a MAPOS network can provide transparent point-to-point link for PPP over SONET/SDH (Packet over SONET/SDH, POS) without any additional overhead.
本文件规定了MAPOS（SONET/SDH上的多址协议）网络上的隧道配置。使用此模式，MAPOS网络可以为SONET/SDH上的PPP（SONET/SDH上的数据包，POS）提供透明的点对点链路，而无需任何额外开销。
MAPOS [1][2] frame is designed to be similar to PPP over SONET/SDH (Packet over SONET/SDH, POS)[3][4] frame (Figure 1).
MAPOS[1][2]帧的设计类似于SONET/SDH上的PPP（SONET/SDH上的数据包，POS）[3][4]帧（图1）。
a) MAPOS frame header (version 1)
+-----------+-----------+-----------+-----------+
| Address | Control | Protocol |
| 8 bits | fixed,0x03| 16 bits |
+-----------+-----------+-----------+-----------+
a) MAPOS frame header (version 1)
+-----------+-----------+-----------+-----------+
| Address | Control | Protocol |
| 8 bits | fixed,0x03| 16 bits |
+-----------+-----------+-----------+-----------+
b) MAPOS frame header (MAPOS 16)
+-----------+-----------+-----------+-----------+
| Address | Protocol |
| 16bits | 16 bits |
+-----------+-----------+-----------+-----------+
b) MAPOS frame header (MAPOS 16)
+-----------+-----------+-----------+-----------+
| Address | Protocol |
| 16bits | 16 bits |
+-----------+-----------+-----------+-----------+
c) PPP frame header
+-----------+-----------+-----------+-----------+
| Address | Control | Protocol |
| fixed,0xFF| fixed,0x03| 16 bits |
+-----------+-----------+-----------+-----------+
c) PPP frame header
+-----------+-----------+-----------+-----------+
| Address | Control | Protocol |
| fixed,0xFF| fixed,0x03| 16 bits |
+-----------+-----------+-----------+-----------+
Figure 1. Header similarity of MAPOS frame and POS frame
图1。MAPOS框架和POS框架的头部相似性
This means that a MAPOS network can easily carry POS frames with no additional header overhead by rewriting only 1 or 2 octets. PPP tunneling configuration over MAPOS networks (MAPOS/PPP tunneling mode) provides for efficient L2 multiplexing by which users can share the cost of high speed long-haul links.
这意味着，通过只重写1或2个八位字节，MAPOS网络可以轻松地承载POS帧，而无需额外的报头开销。MAPOS网络上的PPP隧道配置（MAPOS/PPP隧道模式）提供了高效的L2多路复用，用户可以通过这种方式分担高速长途链路的成本。
This document specifies MAPOS/PPP tunneling mode. In this mode, a MAPOS network provides a point-to-point link for those who intend to connect POS equipment. Such link is established within a MAPOS switch, or between a pair of MAPOS switches that converts between POS header and MAPOS header for each L2 frame.
本文件规定了MAPOS/PPP隧道模式。在此模式下，MAPOS网络为打算连接POS设备的用户提供点对点链接。这种链接建立在一个MAPOS交换机内，或在一对MAPOS交换机之间，该对MAPOS交换机为每个L2帧在POS报头和MAPOS报头之间进行转换。
Chapter 2 describes the specification in two parts. First part is user network interface (UNI) specification and the second part is operation, administration, management and provisioning (OAM&P) description. Other issues such as congestion avoidance, end-to-end fairness control are out of scope of this document.
第2章分两部分描述了规范。第一部分是用户网络接口（UNI）规范，第二部分是操作、管理、管理和资源调配（OAM&P）说明。其他问题，如拥塞避免、端到端公平性控制，不在本文档范围内。
Implementation issues are discussed in Chapter 3. Security considerations are noted in Chapter 4.
第3章讨论了实施问题。安全注意事项见第4章。
MAPOS/PPP tunneling mode is based on header rewriting. Figure 2. shows an example of MAPOS/PPP tunneling mode. The MAPOS network uses MAPOS 16 [2] in this example. Consider a tunneling path between customer premise equipment (CPE) A and CPE B which are industry standard POS equipment. The ingress/egress MAPOS switches A/B assigns unique MAPOS addresses (0x0203 and 0x0403) to the CPEs. These MAPOS addresses are used in the MAPOS network, for frame forwarding between CPE A and CPE B. NSP [5] will not be running between the CPEs and the switches in this case.
MAPOS/PPP隧道模式基于头重写。图2。显示了MAPOS/PPP隧道模式的示例。在本例中，MAPOS网络使用MAPOS 16[2]。考虑客户驻地设备（CPE）A和CPE B之间的隧道路径，CPE B是行业标准POS设备。入口/出口MAPOS开关A/B为CPE分配唯一的MAPOS地址（0x0203和0x0403）。这些MAPOS地址用于MAPOS网络中，用于CPE A和CPE B之间的帧转发。在这种情况下，NSP[5]将不会在CPE和交换机之间运行。
MAPOS switch A rewrites the first 2 octets of every frame from CPE A, which are fixed as 0xFF and 0x03, to the MAPOS address of its peer, which is 0x0403. Frames are forwarded by the MAPOS network and arrives at the egress MAPOS switch B which rewrites the first 2 octets to their original values. If MAPOS v1 [1] is used in the MAPOS network, only the first octet is rewritten.
MAPOS交换机A将CPE A（固定为0xFF和0x03）中每帧的前2个八位字节重写到其对等方的MAPOS地址0x0403。帧由MAPOS网络转发并到达出口MAPOS交换机B，该交换机将前2个八位字节重写为其原始值。如果在MAPOS网络中使用MAPOS v1[1]，则仅重写第一个八位组。
+-----+ POS/0x0203 +--------+ +--------+
|CPE A|<---------->|MAPOS | MAPOS |MAPOS |<---
+-----+ --->|switch A|------------------|switch |<---
+--------+\__ Network __/ +--------+
\__ __/
+--------+ +-|-----|-+ POS/0x0403 +-----+
--->|MAPOS |----|MAPOS |<---------->|CPE B|
--->|switch | |switch B |<--- +-----+
+--------+ +---------+
+-----+ POS/0x0203 +--------+ +--------+
|CPE A|<---------->|MAPOS | MAPOS |MAPOS |<---
+-----+ --->|switch A|------------------|switch |<---
+--------+\__ Network __/ +--------+
\__ __/
+--------+ +-|-----|-+ POS/0x0403 +-----+
--->|MAPOS |----|MAPOS |<---------->|CPE B|
--->|switch | |switch B |<--- +-----+
+--------+ +---------+
Figure 2. MAPOS/PPP tunneling mode
图2。MAPOS/PPP隧道模式
The tunneling path between the two CPEs is managed by the ingress/egress MAPOS switches.
两个CPE之间的隧道路径由入口/出口MAPOS交换机管理。
For transport media between border MAPOS switch and CPE, SONET/SDH signal is utilized. Signal speed, path signal label, light power budget and all physical requirements are the same as those of PPP over SONET/SDH [3].
对于边界MAPOS交换机和CPE之间的传输介质，使用SONET/SDH信号。信号速度、路径信号标签、光功率预算和所有物理要求与SONET/SDH上的PPP相同[3]。
SONET/SDH overheads are terminated at the ingress/egress switches. SONET/SDH performance monitors and alarms are used for the link management between a CPE and the switch. Inter-switch links are similarly managed by SONET/SDH monitors and alarms.
SONET/SDH开销在入口/出口交换机处终止。SONET/SDH性能监视器和警报用于CPE和交换机之间的链路管理。交换机间链路同样由SONET/SDH监视器和警报管理。
A CPE should synchronize to the clock of the border MAPOS switch. The corresponding port of the MAPOS switch uses its internal clock. When the CPE is connected to the MAPOS switch through SONET/SDH transmission equipment, both should synchronize to the clock of the SONET/SDH transmission equipment.
CPE应与border MAPOS交换机的时钟同步。MAPOS交换机的相应端口使用其内部时钟。当CPE通过SONET/SDH传输设备连接到MAPOS交换机时，两者都应与SONET/SDH传输设备的时钟同步。
Link layer framing between CPE and MAPOS switch also follows the specification of PPP over SONET/SDH [3].
CPE和MAPOS交换机之间的链路层帧也遵循SONET/SDH上的PPP规范[3]。
HDLC operation including byte stuffing, scrambling, FCS generation is terminated at the ingress/egress switch. In a MAPOS switch, HDLC frame [4] is picked up from a SONET/SDH payload and the first octet (HDLC address) for MAPOS v1 [1], or the first two octets (HDLC address and control field) for MAPOS 16 [2] are rewritten. The operation inside the border switch is as follows:
HDLC操作（包括字节填充、加扰、FCS生成）在入口/出口交换机处终止。在MAPOS交换机中，HDLC帧[4]从SONET/SDH有效载荷中拾取，并重写MAPOS v1[1]的第一个八位组（HDLC地址），或MAPOS 16[2]的前两个八位组（HDLC地址和控制字段）。边界开关内的操作如下所示：
From CPE (Ingress Switch receiving):
来自CPE（入口开关接收）：
SONET/SDH framing
-> X^43+1 De-scrambling -> HDLC Byte de-stuffing
-> HDLC FCS detection (if error, silently discard)
-> L2 HDLC address/control rewriting
(0xFF -> MAPOS v1 destination address, or
0xFF03 -> MAPOS 16 destination address)
-> MAPOS-FCS generation
-> HDLC Byte stuffing -> X^43+1 Scrambling -> SONET/SDH framing
SONET/SDH framing
-> X^43+1 De-scrambling -> HDLC Byte de-stuffing
-> HDLC FCS detection (if error, silently discard)
-> L2 HDLC address/control rewriting
(0xFF -> MAPOS v1 destination address, or
0xFF03 -> MAPOS 16 destination address)
-> MAPOS-FCS generation
-> HDLC Byte stuffing -> X^43+1 Scrambling -> SONET/SDH framing
To CPE (Egress Switch transmitting):
至CPE（出口开关传输）：
SONET/SDH framing
-> X^43+1 De-scrambling -> HDLC Byte de-stuffing
-> MAPOS-FCS detection (if error, silently discard)
-> L2 HDLC address/control rewriting
(MAPOS v1 address -> 0xFF, or
MAPOS 16 address -> 0xFF03)
-> HDLC FCS generation
-> HDLC Byte stuffing -> X^43+1 Scrambling -> SONET/SDH framing
SONET/SDH framing
-> X^43+1 De-scrambling -> HDLC Byte de-stuffing
-> MAPOS-FCS detection (if error, silently discard)
-> L2 HDLC address/control rewriting
(MAPOS v1 address -> 0xFF, or
MAPOS 16 address -> 0xFF03)
-> HDLC FCS generation
-> HDLC Byte stuffing -> X^43+1 Scrambling -> SONET/SDH framing
For STS-3c-SPE/VC-4, non-scrambled frame can be used for compatibility with RFC 1619. However, the use of 32bit-CRC and X^43+1 scrambling is recommended in RFC2615 [3] and for MAPOS networks.
对于STS-3c-SPE/VC-4，非加扰帧可用于与RFC 1619兼容。但是，RFC2615[3]和MAPOS网络建议使用32位CRC和X^43+1加扰。
Maximum transmission unit (MTU) of the link must not be negotiated larger than MAPOS-MTU which is 65280 octets.
链路的最大传输单元（MTU）不得大于MAPOS-MTU，即65280个八位字节。
Figure 3 shows a CPE-side L2 frame and the converted frame in the ingress/egress MAPOS switches. Note that the MAPOS/PPP tunneling mode is not a piggy-back encapsulation, but it is a transparent link with no additional header overhead.
图3显示了入口/出口MAPOS交换机中的CPE侧L2帧和转换后的帧。请注意，MAPOS/PPP隧道模式不是一种背驮式封装，而是一种透明链接，没有额外的头开销。
<--- Transmission
+----------+----------+----------+----------+
| Flag | Address | Control | Protocol |
| 01111110 | 11111111 | 00000011 | 16 bits |
+----------+----------+----------+----------+
+-------------+---------+----------+----------+-----------------
| Information | Padding |HDLC FCS | Flag | Inter-frame Fill
| * | * |16/32 bits| 01111110 | or next Address
+-------------+---------+----------+----------+-----------------
<--- Transmission
+----------+----------+----------+----------+
| Flag | Address | Control | Protocol |
| 01111110 | 11111111 | 00000011 | 16 bits |
+----------+----------+----------+----------+
+-------------+---------+----------+----------+-----------------
| Information | Padding |HDLC FCS | Flag | Inter-frame Fill
| * | * |16/32 bits| 01111110 | or next Address
+-------------+---------+----------+----------+-----------------
(a) HDLC frame from/to CPE
(a) 从CPE到CPE的HDLC帧
<--- Transmission
+----------+----------+----------+----------+
| Flag | MAPOS Destination | Protocol |
| 01111110 | 0xxxxxx0 | xxxxxxx1 | 16 bits |
+----------+----------+----------+----------+
+-------------+---------+----------+----------+-----------------
| Information | Padding |MAPOS FCS | Flag | Inter-frame Fill
| * | * |16/32 bits| 01111110 | or next Address
+-------------+---------+----------+----------+-----------------
<--- Transmission
+----------+----------+----------+----------+
| Flag | MAPOS Destination | Protocol |
| 01111110 | 0xxxxxx0 | xxxxxxx1 | 16 bits |
+----------+----------+----------+----------+
+-------------+---------+----------+----------+-----------------
| Information | Padding |MAPOS FCS | Flag | Inter-frame Fill
| * | * |16/32 bits| 01111110 | or next Address
+-------------+---------+----------+----------+-----------------
(b) Converted MAPOS 16 frame, forwarded in MAPOS networks
(b) 转换的MAPOS 16帧，在MAPOS网络中转发
Figure 3. HDLC frame from/to CPE and its conversion
图3。HDLC帧从CPE到CPE及其转换
When a port of MAPOS switch is configured to PPP tunneling mode, at least the following operations are performed in the switch.
当MAPOS交换机的端口配置为PPP隧道模式时，交换机中至少会执行以下操作。
a) Disable NSP [5] and SSP [6] (for the port, same below) b) Disable MAPOS broadcast and multicast forwarding
a) 禁用NSP[5]和SSP[6]（对于端口，下同）b）禁用MAPOS广播和多播转发
c) Reset the Path Signal Label (C2) to 0x16 if X^43+1 scrambling is used. The value 0xCF is used for non-scrambled OC3c signal. d) Enable header rewriting function to specified destination address
c) 如果使用X^43+1加扰，则将路径信号标签（C2）重置为0x16。值0xCF用于非加扰OC3c信号。d） 对指定的目标地址启用标头重写功能
When the port is configured back to MAPOS mode, reverse order of the operations above are performed. That means;
当端口配置回MAPOS模式时，执行与上述操作相反的顺序。这意味着；
a) Disable header rewriting function (for the port, same below) b) Reset the Path Signal Label (C2) to MAPOS default (0x8d) c) Enable MAPOS broadcast and multicast forwarding d) Enable NSP and SSP
a) 禁用报头重写功能（对于端口，下同）b）将路径信号标签（C2）重置为MAPOS默认值（0x8d）c）启用MAPOS广播和多播转发d）启用NSP和SSP
SONET/SDH alarms (B1/B2/B3 error exceeding, SLOF, SLOS, etc.) should not affect this transition. Figure 4 shows mode transition described above.
SONET/SDH警报（B1/B2/B3错误超过、SLOF、SLO等）不应影响此转换。图4显示了上述模式转换。
[MAPOS mode] <----------------------------+
| |
(Disable NSP) (Enable NSP)
(Disable SSP) (Enable SSP)
(Disable Broadcast/ (Enable Broadcast/
Multicast forwarding) Multicast forwarding)
(C2-byte setting to 0x16 or 0xcf) (C2-byte setting to 0x8d)
(Enable Header Rewriting function) (Disable Header Rewriting
| | function)
v |
[PPP mode] --------------------------------+
[MAPOS mode] <----------------------------+
| |
(Disable NSP) (Enable NSP)
(Disable SSP) (Enable SSP)
(Disable Broadcast/ (Enable Broadcast/
Multicast forwarding) Multicast forwarding)
(C2-byte setting to 0x16 or 0xcf) (C2-byte setting to 0x8d)
(Enable Header Rewriting function) (Disable Header Rewriting
| | function)
v |
[PPP mode] --------------------------------+
Figure 4. MAPOS/PPP tunneling mode state transition diagram
图4。MAPOS/PPP隧道模式状态转换图
A MAPOS/PPP tunneling path is established by following steps.
通过以下步骤建立MAPOS/PPP隧道路径。
a) Choose MAPOS address pair on both ingress/egress switches and configure their ports to PPP tunneling mode (see 2.3.1).
a) 在两个入口/出口交换机上选择MAPOS地址对，并将其端口配置为PPP隧道模式（见2.3.1）。
b) When the routes for both directions become stable, the tunneling path is established. The link between the CPEs may be set up at that moment; PPP LCP controls are transparently exchanged by the CPEs.
b) 当两个方向的路线变得稳定时，隧道路径就建立起来。此时可建立CPE之间的链路；PPP LCP控制由CPE透明地交换。
To add a new path, operators should pick unused MAPOS address-pair. They may be determined simply by choosing switches and ports for each CPE, because there is one-to-one correspondence between MAPOS addresses and switch ports.
要添加新路径，操作员应选择未使用的MAPOS地址对。它们可以简单地通过为每个CPE选择交换机和端口来确定，因为MAPOS地址和交换机端口之间存在一对一的对应关系。
Then, those ports should be configured to MAPOS/PPP tunneling mode on both of the switches. Frame reachability is provided by SSP [6] in the MAPOS network. When the frame forwarding for each direction are stable, the path is established and frame forwarding is started. Until then, the link between border switches and CPE should be down.
然后，这些端口应配置为两台交换机上的MAPOS/PPP隧道模式。帧可达性由MAPOS网络中的SSP[6]提供。当每个方向的帧转发稳定时，建立路径并开始帧转发。在此之前，边界交换机和CPE之间的链路应该断开。
A MAPOS/PPP tunneling path should be managed by the pair of MAPOS addresses. It should be carefully handled to avoid misconfiguration such as path duplication. For convenient management, path database can be used to keep information about pairs of MAPOS addresses. Note that the path database is not used for frame forwarding. It is for OAM&P use only.
MAPOS/PPP隧道路径应由一对MAPOS地址管理。应小心处理，以避免错误配置，例如路径重复。为了便于管理，可以使用path数据库保存有关MAPOS地址对的信息。请注意，路径数据库不用于帧转发。它仅供OAM&P使用。
When any link or node failure is detected, it should be indicated to each peer of the path. This is done by PPP [7] keep-alive (LCP Echo request/reply) for end-to-end detection.
当检测到任何链路或节点故障时，应将其指示给路径的每个对等方。这是由PPP[7]保持活动（LCP回送请求/回复）完成的，用于端到端检测。
Consideration is required to handle SONET/SDH alarms. When a link between CPE and the MAPOS switch fails, it is detected by both the MAPOS switch and the CPE seeing SONET/SDH alarms. However, far-side link remains up and no SONET/SDH error is found; SONET/SDH alarms are not transferred to the far end because each optical path is terminated in MAPOS network. In this case, the far end will see 'link up, line protocol down' status due to keep-alive expiration.
需要考虑处理SONET/SDH警报。当CPE和MAPOS交换机之间的链路出现故障时，MAPOS交换机和CPE都会检测到SONET/SDH警报。然而，远侧链路保持正常，未发现SONET/SDH错误；SONET/SDH警报不会传输到远端，因为每条光路都在MAPOS网络中终止。在这种情况下，由于保持活动到期，远端将看到“链路接通，线路协议断开”状态。
For example, Figure 5 shows a tunneling path. When link 1 goes down, MAPOS sw A and CPE A detects SONET/SDH alarms but MAPOS sw B and CPE A' do not see this failure. When PPP keep-alive expires, CPE A' detects the failure and stops the packet transmission. The same mechanism is used for failure within the MAPOS cloud (link 2). When a MAPOS switch is down, SSP handles it as a topology change.
例如，图5显示了一个隧道路径。链路1断开时，MAPOS sw A和CPE A检测到SONET/SDH警报，但MAPOS sw B和CPE A“未发现此故障”。当PPP保持活动到期时，CPE A'检测到故障并停止数据包传输。MAPOS云中的故障也使用相同的机制（链接2）。当MAPOS交换机关闭时，SSP将其作为拓扑更改处理。
1 2 3
CPE A <-x-> MAPOS sw A ---(MAPOS cloud)--- MAPOS sw B <---> CPE A'
1 2 3
CPE A <-x-> MAPOS sw A ---(MAPOS cloud)--- MAPOS sw B <---> CPE A'
Figure 5. Link failure
图5。链路故障
2.3.4 Path removal
2.3.4 路径移除
A MAPOS/PPP tunneling path is removed by following steps.
通过以下步骤删除MAPOS/PPP隧道路径。
a) Choose the path to remove, configure MAPOS switches on both ends of the path to disable the ports connected to the CPEs.
a) 选择要删除的路径，在路径两端配置MAPOS交换机以禁用连接到CPE的端口。
b) Path database may be updated that the path is removed.
b) 可能会更新路径数据库以删除该路径。
c) When CPE is detached, port may be reset to MAPOS default configurations.
c) 当CPE分离时，端口可能会重置为MAPOS默认配置。
Frames arriving after the destination port was disabled should be silently discarded and should not be forwarded to the port.
在禁用目标端口后到达的帧应被静默丢弃，并且不应转发到该端口。
Because MAPOS does not have any QoS control at its protocol level, and POS does not have flow-control feature, it is difficult to guarantee end-end throughput. Sufficient bandwidth for inter-switch link should be prepared to support all paths on the link.
由于MAPOS在其协议级别没有任何QoS控制，并且POS没有流量控制功能，因此很难保证终端吞吐量。应为交换机间链路准备足够的带宽，以支持链路上的所有路径。
Switches are recommended to ensure per-port fairness using any appropriate queuing algorithm. This is especially important for over-subscribed configuration, for example to have more than 16 OC12c paths on one OC192c inter-switch link.
建议交换机使用任何适当的排队算法来确保每个端口的公平性。这对于过度订阅的配置尤其重要，例如，在一个OC192c交换机间链路上有超过16条OC12c路径。
Although MAPOS v1 can be applied to the MAPOS/PPP tunneling mode, MAPOS 16 is recommended for ease of address management.
虽然MAPOS v1可以应用于MAPOS/PPP隧道模式，但为了便于地址管理，建议使用MAPOS 16。
Automatic switch address negotiation mechanism is not suitable for the MAPOS/PPP tunneling mode, because the path management mechanism becomes much more complex.
自动交换地址协商机制不适用于MAPOS/PPP隧道模式，因为路径管理机制变得更加复杂。
Figure 6 shows an example of MAPOS network with four switches. Inter-switch links are provided at OC192c and OC48c rate, customer links are either OC3c or OC12c rate. Some links are optically protected. Path database is used for path management.
图6显示了带有四个交换机的MAPOS网络示例。交换机间链路以OC192c和OC48c速率提供，客户链路为OC3c或OC12c速率。有些链接受到光学保护。路径数据库用于路径管理。
Using MAPOS-netmask with 8 bits, this topology can be extended up to 64 MAPOS switches, each equipped with up to 127 CPE ports. Switch addresses are fixed to pre-assigned values.
使用8位的MAPOS网络掩码，此拓扑可以扩展到64个MAPOS交换机，每个交换机最多配备127个CPE端口。开关地址固定为预先指定的值。
The cost of optical protection (< 50ms) can be shared among paths. Unprotected link can also be coupled for more redundancy in case of link failure. SSP provides restoration path within few seconds.
光保护的成本（<50ms）可以在路径之间分摊。在链路故障的情况下，未受保护的链路也可以进行耦合以获得更多冗余。SSP在几秒钟内提供恢复路径。
0x2003+---------+ +---------+ 0x2203
A----->| MAPOS | OC192c(protected) | MAPOS |<-------A'
0x2005| Switch 1|=======================| Switch 2| 0x2205
B----->| 0x2000/8| _________| 0x2200/8|<-------C'
+---------+ / +---------+
OC192c| /
| / OC48c(backup)
+---------+ / +---------+ 0x2603
| MAPOS |_________/ | MAPOS |<-------B'
0x2405| Switch 3|=======================| Switch 4|
C----->| 0x2400/8| OC192c(protected) | 0x2600/8|
+---------+ +---------+
0x2003+---------+ +---------+ 0x2203
A----->| MAPOS | OC192c(protected) | MAPOS |<-------A'
0x2005| Switch 1|=======================| Switch 2| 0x2205
B----->| 0x2000/8| _________| 0x2200/8|<-------C'
+---------+ / +---------+
OC192c| /
| / OC48c(backup)
+---------+ / +---------+ 0x2603
| MAPOS |_________/ | MAPOS |<-------B'
0x2405| Switch 3|=======================| Switch 4|
C----->| 0x2400/8| OC192c(protected) | 0x2600/8|
+---------+ +---------+
Path database entries:
-----------------------------------------------------------
User : Speed : Mode : Address pair : Status
-----------------------------------------------------------
A-A' : OC3c : CRC32, scramble : 0x2003-0x2203 : Up and running
B-B' : OC12c : CRC32, scramble : 0x2005-0x2603 : B Down
C-C' : OC3c : CRC16, no-scram : 0x2405-0x2205 : C' Down
-----------------------------------------------------------
Path database entries:
-----------------------------------------------------------
User : Speed : Mode : Address pair : Status
-----------------------------------------------------------
A-A' : OC3c : CRC32, scramble : 0x2003-0x2203 : Up and running
B-B' : OC12c : CRC32, scramble : 0x2005-0x2603 : B Down
C-C' : OC3c : CRC16, no-scram : 0x2405-0x2205 : C' Down
-----------------------------------------------------------
Figure 6. Example Topology and its Path Management
图6。示例拓扑及其路径管理
Figure 7 shows evaluation platforms in terms of latency measurement of MAPOS/PPP tunneling mode.
图7显示了MAPOS/PPP隧道模式延迟测量方面的评估平台。
Case 1: Base latency measurement
案例1：基本延迟测量
Measurement
Equipment
+---------+ POS Unidirectional Flow, OC12c 30%, FCS 32bits,
| IXIA 400| payload-scrambling on (same for all cases)
| POS-LM |<--+
| OC12c x2|---+ Loopback
+---------+
(Using IxSoftware v3.1.148/SP1d)
Measurement
Equipment
+---------+ POS Unidirectional Flow, OC12c 30%, FCS 32bits,
| IXIA 400| payload-scrambling on (same for all cases)
| POS-LM |<--+
| OC12c x2|---+ Loopback
+---------+
(Using IxSoftware v3.1.148/SP1d)
Case 2: Router latency measurement
案例2：路由器延迟测量
Measurement Device Under Test
+---------+ POS +------------+
| IXIA 400| Unidirectional Flow | Cisco GSR |
| POS-LM |<---------------------| 12008/1port|
| OC12c x2|--------------------->| OC12cLC x2 |
+---------+ +------------+
(Using IOS 12.0(15)S1)
Measurement Device Under Test
+---------+ POS +------------+
| IXIA 400| Unidirectional Flow | Cisco GSR |
| POS-LM |<---------------------| 12008/1port|
| OC12c x2|--------------------->| OC12cLC x2 |
+---------+ +------------+
(Using IOS 12.0(15)S1)
Case 3: MAPOS/PPP tunneling switch latency measurement
案例3:MAPOS/PPP隧道交换机延迟测量
Measurement Device Under Test
+---------+ POS +-------------+
| IXIA 400| Unidirectional Flow | CSR MAPOS |
| POS-LM |<---------------------| CORESwitch80|
| OC12c x2|--------------------->| OC12c x2 |
+---------+ +-------------+
Measurement Device Under Test
+---------+ POS +-------------+
| IXIA 400| Unidirectional Flow | CSR MAPOS |
| POS-LM |<---------------------| CORESwitch80|
| OC12c x2|--------------------->| OC12c x2 |
+---------+ +-------------+
Figure 7. Latency measurement of reference platform for MAPOS/PPP tunneling mode
图7。MAPOS/PPP隧道模式参考平台的延迟测量
There is a PPP connection between port 1 and 2 of the measurement equipment. Traffic comes from measurement equipment (IXIA 400) and forwarded by a device under test back to the equipment. Timestamping and latency calculation are performed by IXIA 400 automatically. Traffic Load is set to 30% of OC12c for offloading router.
测量设备的端口1和端口2之间存在PPP连接。流量来自测量设备（IXIA 400），并由被测设备转发回设备。时间戳和延迟计算由IXIA 400自动执行。流量负载设置为OC12c的30%，用于卸载路由器。
Results are shown in Table 1. Measurements were taken according to the RFC2544 requirements [8]. We measured 25 trials of 150 seconds duration for each frame size. Results are averaged and rounded to the 20 ns resolution of IXIA. 95% confidence interval (C.I.) value are also rounded.
结果如表1所示。根据RFC2544要求进行测量[8]。我们测量了25个试验，每个帧大小持续150秒。结果取平均值并四舍五入至IXIA的20 ns分辨率。95%置信区间（C.I.）值也四舍五入。
--------------------------------------------------------------------
Frame size (bytes) 64 128 256 512 1024 1280 1518
--------------------------------------------------------------------
Latency(ns)
--------------------------------------------------------------------
Case 1: Baseline 4060 5640 6940 9840 16420 20700 23340
95% C.I.(+/-) 20 80 60 180 80 100 120
--------------------------------------------------------------------
Case 2: Router 26560 28760 33860 44600 68280 80500 91160
95% C.I.(+/-) 200 100 160 220 100 100 200
--------------------------------------------------------------------
Case 3: Switch 11100 13480 16620 22920 36380 43900 49920
95% C.I.(+/-) 120 120 120 200 100 160 120
--------------------------------------------------------------------
Table 1. Results of Latency (ns) - Frame size (bytes)
--------------------------------------------------------------------
Frame size (bytes) 64 128 256 512 1024 1280 1518
--------------------------------------------------------------------
Latency(ns)
--------------------------------------------------------------------
Case 1: Baseline 4060 5640 6940 9840 16420 20700 23340
95% C.I.(+/-) 20 80 60 180 80 100 120
--------------------------------------------------------------------
Case 2: Router 26560 28760 33860 44600 68280 80500 91160
95% C.I.(+/-) 200 100 160 220 100 100 200
--------------------------------------------------------------------
Case 3: Switch 11100 13480 16620 22920 36380 43900 49920
95% C.I.(+/-) 120 120 120 200 100 160 120
--------------------------------------------------------------------
Table 1. Results of Latency (ns) - Frame size (bytes)
This results shows that MAPOS/PPP tunneling mode does not cause any performance degradation in terms of latency view. A POS L2 switch was reasonably faster than a L3 router.
该结果表明，MAPOS/PPP隧道模式不会导致延迟视图方面的任何性能下降。POS L2交换机比L3路由器快得多。
There is no way to control or attack a MAPOS network from CPE side under PPP tunneling mode. It is quite difficult to inject other stream because it is completely transparent from the viewpoint of the CPE. However, operators must carefully avoid misconfiguration such as path duplication. Per-path isolation is extremely important; switches are recommended to implement this feature (like VLAN mechanism).
在PPP隧道模式下，无法从CPE端控制或攻击MAPOS网络。注入其他流是相当困难的，因为从CPE的观点来看，它是完全透明的。但是，操作员必须小心避免错误配置，例如路径重复。每路径隔离非常重要；建议交换机实现此功能（如VLAN机制）。
In addition, potential vulnerability still exists in a mixed environment where PPP tunneling mode and MAPOS native mode coexists in the same network. Use of such environment is not recommended, until an isolation feature is implemented in all MAPOS switches in the network. Note that there is no source address field in the MAPOS framing, which may make path isolation difficult in a mixed MAPOS/PPP environment.
此外，在PPP隧道模式和MAPOS本机模式共存于同一网络的混合环境中，仍然存在潜在漏洞。在网络中的所有MAPOS交换机中实现隔离功能之前，不建议使用此类环境。请注意，MAPOS帧中没有源地址字段，这可能会使混合MAPOS/PPP环境中的路径隔离变得困难。
[1] Murakami, K. and M. Maruyama, "MAPOS - Multiple Access Protocol over SONET/SDH Version 1", RFC 2171, June 1997.
[1] Murakami，K.和M.Maruyama，“MAPOS-SONET/SDH版本1上的多址协议”，RFC 2171，1997年6月。
[2] Murakami, K. and M. Maruyama, "MAPOS 16 - Multiple Access Protocol over SONET/SDH with 16 Bit Addressing", RFC 2175, June 1997.
[2] Murakami，K.和M.Maruyama，“MAPOS 16-SONET/SDH上具有16位寻址的多址协议”，RFC 2175，1997年6月。
[3] Malis, A. and W. Simpson, "PPP over SONET/SDH", RFC 2615, June 1999.
[3] Malis，A.和W.Simpson，“SONET/SDH上的PPP”，RFC 26151999年6月。
[4] Simpson, W., "PPP in HDLC-like Framing", STD 51, RFC 1662, July 1994.
[4] 辛普森，W.“HDLC类框架中的PPP”，STD 51，RFC 16621994年7月。
[5] Murakami, K. and M. Maruyama, "A MAPOS version 1 Extension - Node Switch Protocol," RFC 2173, June 1997.
[5] Murakami，K.和M.Maruyama，“MAPOS版本1扩展-节点切换协议”，RFC21731997年6月。
[6] Murakami, K. and M. Maruyama, "A MAPOS version 1 Extension - Switch-Switch Protocol", RFC 2174, June 1997.
[6] Murakami，K.和M.Maruyama，“MAPOS版本1扩展-交换协议”，RFC2174，1997年6月。
[7] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, RFC 1661, July 1994.
[7] 辛普森，W.，“点对点协议（PPP）”，STD 51，RFC 1661994年7月。
[8] Bradner, S. and J. McQuaid, "Benchmarking Methodology for Network Interconnect Devices", RFC 2544, March 1999.
[8] Bradner，S.和J.McQuaid，“网络互连设备的基准测试方法”，RFC 25441999年3月。
The authors would like to acknowledge the contributions and thoughtful suggestions of Takahiro Sajima.
作者要感谢三岛隆弘的贡献和深思熟虑的建议。
Susumu Shimizu NTT Network Innovation Laboratories, 3-9-11, Midori-cho Musashino-shi Tokyo 180-8585 Japan
Susumu Shimizu NTT网络创新实验室，3-9-11，Midori cho Musashino shi东京180-8585
Phone: +81 422 59 3323
Fax: +81 422 59 3765
EMail: shimizu@ntt-20.ecl.net
Phone: +81 422 59 3323
Fax: +81 422 59 3765
EMail: shimizu@ntt-20.ecl.net
Tetsuo Kawano NTT Network Innovation Laboratories, 3-9-11, Midori-cho Musashino-shi Tokyo 180-8585 Japan
河野铁雄NTT网络创新实验室，3-9-11，日本东京武藏市中多里町180-8585
Phone: +81 422 59 7145
Fax: +81 422 59 4584
EMail: kawano@core.ecl.net
Phone: +81 422 59 7145
Fax: +81 422 59 4584
EMail: kawano@core.ecl.net
Ken Murakami NTT Network Innovation Laboratories, 3-9-11, Midori-cho Musashino-shi Tokyo 180-8585 Japan
Ken Murakami NTT网络创新实验室，3-9-11，Midori cho Musashino shi东京180-8585
Phone: +81 422 59 4650
Fax: +81 422 59 3765
EMail: murakami@ntt-20.ecl.net
Phone: +81 422 59 4650
Fax: +81 422 59 3765
EMail: murakami@ntt-20.ecl.net
Eduard Beier DeTeSystem GmbH Merianstrasse 32 D-90409 Nuremberg, Germany
Eduard Beier DeTeSystem GmbH Merianstrasse 32 D-90409德国纽伦堡
EMail: Beier@bina.de
EMail: Beier@bina.de
Copyright (C) The Internet Society (2001). All Rights Reserved.
版权所有（C）互联网协会（2001年）。版权所有。
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.
本文件及其译本可复制并提供给他人，对其进行评论或解释或协助其实施的衍生作品可全部或部分编制、复制、出版和分发，不受任何限制，前提是上述版权声明和本段包含在所有此类副本和衍生作品中。但是，不得以任何方式修改本文件本身，例如删除版权通知或对互联网协会或其他互联网组织的引用，除非出于制定互联网标准的需要，在这种情况下，必须遵循互联网标准过程中定义的版权程序，或根据需要将其翻译成英语以外的其他语言。
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
上述授予的有限许可是永久性的，互联网协会或其继承人或受让人不会撤销。
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
本文件和其中包含的信息是按“原样”提供的，互联网协会和互联网工程任务组否认所有明示或暗示的保证，包括但不限于任何保证，即使用本文中的信息不会侵犯任何权利，或对适销性或特定用途适用性的任何默示保证。
Acknowledgement
确认
Funding for the RFC Editor function is currently provided by the Internet Society.
RFC编辑功能的资金目前由互联网协会提供。